Chimney jacks



March 29, 1955 G. w. MONLUX 2,704,972

CHIMNEY JACKS Filed March 31, 1952 2 Sheets-Sheet 1 1M 'EN TOR. 450E615 14/ MOA/ZUX dV iZeA QMQKW March 29, 1955 G. w. MONLUX 2,704,972

CHIMNEY JACKS Filed March 31, l92 2 Sheets-Sheet 2 y INVENTOR. 660/966 14/ MOA/ZUX United States Patent CHIMNEY JACKS George W. Monlux, North Bend, Wash. Application March 31, 1952, Serial No. 279,654

9 Claims. (Cl. 98-78) This invention relates to chimney jacks and is herein illustratively described by reference to the preferred form thereof as intended for application to conventional domestic dwelling chimneys, but it will be evident that certain modifications therein may be made without departing from the underlying essential features involved.

A chief purpose of chimney jacks in general is, of course, the extension of chimney flue height and thereby the strengthening of draft through the furnace, fireplace or other combustion device. With this objective have been combined various others in different previously proposed chimney jacks, including the shedding of precipitation and the elimination of down drafts. Complicating factors, such as the effects of side winds, have arisen, however, and impaired the operation of most former combined purpose jacks. Moreover, the introduction therein of baflles, covers, deflectors or the like, as previously constructed, has resulted in lowered efficien' of prior types of chimney jacks and caused such undesirable phenomena as oscillating draft pressures and occasionally pocketing of combustion products leading to extinguishment of oil furnace pilot fires and sometimes blow out of soot and gases through fissures in the furnace walls. These and other difliculties experienced in the past have tended to discourage the use of chimney jacks, especially with modern oil or gas burning furnace installations requiring a particularly uniform and fairly strong draft for most eflicient operation.

With the improved chimney jack herein disclosed material increases in operating efiiciency of oil burning furnaces and other combustion devices have been realized, and in particular installations tested, all objectionable blow out conditions, interruption of draft due to back pressures, and flue reverberations due to oscillating draft pressures were overcome. Moreover, because of the special formation and arrangement of jack flue tube side openings and deflector slats, according to the present invention, virtually all precipitation is shed, downdrafts and the effects of side winds are eliminated, and a maximum flue draft increase achieved for a given total height increase supplied by the jack tube. In this latter regard a short but efficient chimney jack is, of course, much preferable to a long one, not only because of its lesser lateral wind load area and potentially lower cost of manufacture and installation, but because most individuals having attractive homes are not readily willing to impair their buildings appearances with an ungainly looking flue extension of excessive length even for the sake of more eflicient flue operation in many instances.

Still other objects of the present invention directed to an improved chimney jack include a relatively simple type of construction lending itself to low cost manufacture in sheet metal form although not necessarily confined to sheet metal, a type of construction which results in a basically simple and architecturally acceptable external appearance unencumbered by unattractive hoods or external covers characteristic of certain prior types, and others which will hereinafter more fully appear.

Described in brief general terms, the improved chimney jack comprised in this invention includes, in its illustrated form, a rectangular elongated flue tube adapted to seat upon the upper lip of the chimney, its breadth and width being approximately determined, therefore, by corresponding chimney flue internal dimensions. On each of two opposite sides of this tube is a generally rectangular opening, each such opening being of a vertical width approximately the tubes width between its opening sides,

Patented Mar. 29, 1955 and the vertical distance separating the two opposite openings being at least as great as such width, and preferably substantially equal thereto. Two upwardly and inwardly sloping parallel deflector slats or baflle strips extend breadthwise of the tube across each side opening therein. One such slat has a horizontally projected area approximately coinciding with the upper half of the respectively adjacent tube side opening and the other such slat bears an approximately similar relationship to the lower half of such opening. The outer, lower edge of the lower slat in each instance is spaced inwardly by a short but material distance from the adjacent side of the flue tube in order to define an exit gap therebetween for escape of flue gases out the side opening. Preferably the two sets of deflector slats, extending at an incline approximately halfway across the tube from its respectively opposite sides, are of concave-upward form, the lower slat in each instance being somewhat trough-shaped so that its lower outer portion defines a narrowing, and thereby eflicient draft throat leading upward into said exit gap, whereas the lower edge of the upper slat of each set slightly overhangs the side of the tube through the opening therein for runolf of rain water dropping into the jack or driven by Wind against its side.

These and other features, objects and advantages of the invention as herein disclosed will become more fully evident from the following detailed description thereof by reference to the accompanying drawings.

Figure 1 is a perspective view of the installed jack having wall portions broken away to show the baffle construction.

Figure 2 is a similar side elevational view.

Figure 3 is a simplified side elevational view at reduced scale illustrating normal operation of the jack.

Figure 4 is a similar view illustrating operation of the jack in a down draft.

Figure 5 is a similar view illustrating operation of the jack in a side wind from the left.

Figure 6 is a similar view illustrating operation of the jack in a side wind from the right.

As shown in Figures 1 and 2, the elongated chimney jack flue tube 10, of generally rectangular cross section, fits down over the lip of the mounting base tube 11 which in turn fits into the chimney stack 12, said base tube having a supporting flange 14 which rests upon the stack 12. A mortar fillet 16 laid around the base tube over the flange and the top of the stack secures it in place. The sheet metal tube 10, of predetermined uniform breadth b and width w, has two opposite side openings therein, one comprising the rectangular opening 18 in the side 20 and the other comprising the rectangular opening 22 in the opposite side 24. Preferably both openings extend the full breadth b of the tube and each is of a vertical Width approximately equal to the width w of the tube 10 between sides 20 and 24. The opening 18 is usually spaced a distance above the opening 22 approximately equal to the tubes width w. The upper edge of the opening 18 is spaced downward from the top of the tube 10 by a material distance preferably in excess of the width w, and the lower edge of opening 22 is spaced upward from the top of the stack 12 by an approximately similar distance w. These latter two distances, and especially the former, may vary with variations in total length of the tube with any extensions thereof, in order to achieve the necessary minimum chimney height extension productive of the needed increase of flue draft pressure in particular cases. However, the vertical distance of separation between the two openings 18 and 22 (i. e. between the heights of their nearest edges) should not vary greatly from the value mentioned for best operation of the jack. In other words this distance of separation should never be appreciably different from the tubes width dimension w and if the tube is longer in one case than in another it is preferred to make up the increase of length by adding length to the upper end of the tube above the upper opening 18. It should be understood, however, that moderate increase of the vertical separation distance mentioned does not critically impair operation of the jack. In order to indicate in Figure 1 that this distance may be moderately increased if desired such distance is dimensioned w+x.

A set of two baffles or deflector slats 26 and 28, upper and lower, respectively, extends breadthwise of the tube 10 across the upper opening 18, and a similar set 30 and 32, in like order and relationship, extends across the lower opening 22. The upper slats 26 and 30. being curved on a progressively increasing incline upwardly and inwardly of the tube from its respectively opposite sides 20 and 24, have lower edges which slightly overhang the lips of the corresponding side openings 18 and 20 in order to shed rain water outwardly past the sides of the tube. These slats extend inwardly at least to the vertical mid-plane of the flue tube 10 parallel to sides 20 and 24, and preferably slightly therebeyond. Their curvature in a perpendicular vertical plane is a gradual curvature of sui'ricient degree to deflect down draft air in the tube 10 efficiently out the side openings adjacent the respective deflector slats, and to deflect side wind air entering such openings efficiently up the flue tube. The horizontal lower edges of slats 26 and 30 are pref erably disposed midway between upper and lower edges of the respective openings 18 and 22 while the upper edges of these slats lie approximately at the horizontal levels of the upper edges of such openings; in other words the horizontally projected area of each such slat approximately coincides with the upper half of the adjacent tube side opening.

The lower deflector slats 28 and 32 of the two sets also extend at a generally upward incline inwardly from the respectively adjacent tube sides to or beyond the parallel vertical mid-plane of the tube. However, the lower or outer edges of these slats are spaced inwardly from the tube sides 18 and 24 by an appreciable distance opposite the lower edges of openings 18 and 22 to define the exit gaps 34 and 36 therebetween, respectively. Preferably these two lower slats of the respective sets are of generally troughlike form, that is their lower or outer portions curve upwardly toward their outer edges nearest the adjacent tube walls so as to define narrowing throats leading into the exit gaps 34 and 36 for efiicient passage out the openings of combustion products rising in the flue tube. However, the reversely inclined inner portions of the two lower slats 28 and 32 have a generally greater slope than the upper slats, so that the upper edges of slats 28 and 32 lie nearer the respective slats 26 and 30 than the lower edges do. Again, the curvature of the slats 28 and 32 in general is such that they function efficiently as air scoops, causing air entering from the adjacent tube side openings to be deflected efficiently upward in the tube 10 and downdraft air in the tube incident upon these I slats to be deflected efficiently out such side openings, that is they deflect the air with minimum turbulence and pocketing. The horizontally projected areas of slats 28 and 32 approximately coincide with the lower halves of the respective openings 18 and 22.

In a typical example, the chimney jack for a standard chimney flue was 8 inches square in cross section and about 36 inches long, extra length if necessary being added by extension sections. The vertical width of openings 18 and 20 in that situation then becomes 8 inches and the vertical distance between the upper edge of opening 22 and the lower edge of opening 18 preferably also 8 inches. The horizontal distance between the upper edge of slat 28 and the tube side 20 was about 4 /2 inches, and the same with respect to slat 30 and tube side 24. The width of the gaps 34 and 36 was 1 /2 inches and the restricted openings between the upper edges of lower slats 28 and 32 and the nearest points on the respective upper slats 26 and 30 was approximately 2 inches. The precise shape of the slats in cross section was not especially critical but the best performance of any shapes tested was achieved with shapes substantially as illustrated and described herein.

As indicated in the drawings the preferred sheet metal construction of the chimney jack involves the utilization of flat rectangular strips for the sides 20 and 24 secured by tack welding to longitudinal edge flanges on the perpendicular side strips. The deflector slats are secured by bent metal tabs to the latter two opposite sides in the manner shown.

Operation of the chimney jack under normal conditions, that is, in still air, is illustrated by the flow-line arrows in Figure 3. The column of gas riding through the base of the flue tube divides below the lowermost deflector slat and part escapes through the gap 36 and out the lower half of opening 22 while the remainder continues to rise in the tube through the space 40 to the left of slat 32. This remaining column of rising gas divides below the deflector slat 28 and part escapes through the gap 34 and out the lower half of opening 18 while the remainder continues to rise in the tube through the space 38 to the right of slat 28. Some outside air is drawn into the tube through the upper halves of the openings 22 and 18 and joins the rising columns of gas emerging from the interior passages 40 and 38 respectively, so that total effective draft created by the chimney jack is not materially depleted by escape or venting through the gaps 36 and 34 below the top of the flue tube 10.

In the event of a down draft into the flue tube as shown in Figure 4 the downwardly moving columns of air incident upon the upper deflector slats 26 and 30 of the two sets are deflected out the adjacent side openings of the tube. However, some of this air passes down through passage 38 to the right of slats 26 and 28 and thereby impedes the normal ascent of some of the hot gases in the tube. These gases are forced to the left beneath lower slat 28. Instead of pocketing there, however, due to a piling up of the two oppositely moving streams of air and gases, the pressure is relieved by escape permitted through gap 34. Gap 36 provides a similar escape for gases tending to be forced by descending air into a pressure pocket beneath lower slat 36. Consequently, while a heavy down draft of air into the top of the flue tube 10 may momentarily block effective or normal flow of combustion products out the very top of the tube, the shielding effect of the lower slats 28 and 32 combined with the presence of the exit gaps 34 and 36 adjacent thereto provides a continuing escape for the rising gases and, to a degree not experienced with former types of chimney jacks, prevents objectionable increase of back pressure in the chimney flue and connected combustion device located in the building below. Extreme flue pressure fluctuations and blowing out in the combustion device below are thereby avoided.

In the event of a sidewind to the right, as in Figure 5, both deflection slats disposed across the inside of the upper opening 18 facing into the wind divert the incoming air through such opening efliciently into a rising column inside the flue tube 10. The lower fringe of the horizontal influx of air as it passes over the lower edges of opening 18 and slat 28 into the tube tends to draw gases up through the gap 34 at an accelerated rate, as a side wind normally draws air from a conventional chimney top, to use through the space between the two slats 26 and 28. To a degree, therefore, this offsets the adverse effect of any tendency for air to pile up in the tube to the right of slats 26 and 28 due to the horizontal influx through opening 18 from such a side wind. Further compensation in the same direction is achieved during a side wind from the left due to the partial vacuum created externally on the right side of the flue tube, drawing combustion products at an accelerated rate out the lower half of opening 22 through exit gap 36. Thus the device continues to functionlesffieiently in a side wind incident upon upper openmg An opposite side wind causing influx of air through lower opening 22 produces a reaction as illustrated in Figure 6. The upwardly directed airstream entering the flue tube produces a similar set of flow conditions around deflector slats 30 and 32 as that described with reference to the slats 26 and 28 in the condition specified for Figure 5. However, in this instance the action surrounding the upper set of deflector slats 26 and 28 warrants special note. There would be a tendency for some of the resultant deflected stream of air rising from the slats 30 and 32 to pocket along the left side of flue tube 10 and especially beneath any deflector slats located on that side of the tube, because some of this air still has a substantial component of motion to the left. The presence of exit gap 34, however, combined with the directing effect of the lower upturned outer portion of slat 28 provides an efficient escape for this pocketing air, which escape is accelerated by the partial vacuum created externally on the left side of the flue tube due to the side wind under consideration. Thus the device continues to function effectively in its intended capacity in a side wind from the right as well as in one from the left and during down winds.

It might at first be thought that the foregoing operating aspects of the improved chimney jack indicate or compel its being mounted on chimneys with one of the side openings 18 or 22 facing into the prevailing wind in the particular area. However, it is found that this is not a necessary precaution and that the device functions satisfactorily without regard to wind direction, due, of course, to the fact that the openings and baflles in tube 10 react to a component of an oblique side wind as effectively as to the entire force of a normal or head-on side wind. The orientatiaon of an existing chimneys sides with respect to prevailing winds is largely uncontrollable in any event, and it is, therefore, a desirable feature of the improved chimney jack that it may be installed and will operate satisfactorily in any and all such cases.

I claim as my invention:

1. A chimney jack comprising an elongated flue tube of predetermined breadth and width adapted for mounting upright on a chimney top, said tube having openings in the opposite sides thereof ofiset vertically, the height of said openings being substantially equal to the width of said tube between such sides, a pair of deflector slats extending breadthwise across the respective openings and being generally inclined upwardly and inwardly from opposite sides of the tube, the lower edges of such deflector slats adjacent the tube sides being located in generally intermediate positions heightwise of their openings respectively, and a second pair of deflector slats extending breadthwise across the respective openings and being generally inclined upwardly and inwardly from opposite sides of said tube, the lower edges of such latter deflector slats being located substantially at the level of the lower edges of the respective tube side openings and being spaced materially inwardly from the tube sides to define an escape gap therebetween for combustion products.

2. The chimney jack defined in claim 1, wherein the first pair of deflector slats curve progressively upwardly from their lower edges and extend at least substantially halfway across the width of the tube, and the second pair of deflector slats slope initially downwardly and inwardly and then curve progressively upwardly and inwardly from their lower edges and extend at least substantially to the middle of the tube.

3. A chimney jack comprising an elongated flue tube of predetermined breadth and width adapted f mounting upright on a chimney top, said tube having a lower lateral opening in one side thereof above its bottom and an upper lateral opening in its opposite side below its top, the height of said openings being substantially equal to the width of said tube between such sides, and the vertical distance between said openings being at least as great as said tube width, a pair of deflector slats extending breadthwise across the respective openings and being generally inclined upwardly and inwardly from opposite sides of the tube, the lower edges of such deflector slats adjacent the tube sides being located in generally intermediate positions heightwise of their openings respectively, and a second pair of deflector slats located below and extending in generally parallel relation to the respective slats of the first pair across said tube side openings and having lower edges spaced materially inwardly from the lower edges of the respective openings.

4. A chimney jack comprising an elongated rectangular flue tube of predetermined breadth and width adapted for mounting upright on a chimney top, said tube having a generally rectangular opening in each of two opposite sides thereof, said openings being vertically E- set from each other by a separating distance of at least approximately the width of the tube between such opposite sides and such openings being of a height approximately equal to said tube width, and two deflector slats extending breadthwise of the tube across each of said openings and inclined upwardly and inwardly, one of said slats having a horizontally projected area coinciding with substantially the upper half of the adjacent opening, and the other of said slats having a horizontally projected area coinciding with substantially the lower half of such opening and having its outer, lower edge spaced materially inwardly from the tube side and defining an exit gap therebetween for escape of combustion products.

5. The chimney jack defined in claim 4, wherein the lower deflector slats adjacent the respective tube side openings are generally trough-shaped and have their inner edges located in the tube materially above their outer, lower edges.

6. The chimney jack defined in claim 4, wherein the lower deflector slats adjacent the respective tube side openings are generally trough-shaped and have their inner edges located in the tube materially above their outer, lower edges, and the upper deflector slats are curved progressively upwardly and inwardly, all of the slats extending inwardly to at least the middle of the tube.

7. A chimney jack comprising an elongated flue tube adapted for mounting upright on a chimney top and having an opening in one side thereof, a deflector slat extending breadthwise across such opening and being gen erally inclined upwardly and inwardly from such opening, and the lower edge of such deflector slat adjacent the tube side being located intermediate between the top and bottom edges of the opening, and a second deflector slat located below and extending in generally parallel relation to the first slat across such opening and having its lower edge approximately level with and spaced a substantial distance inward from the lower edge of the opening.

8. A chimney jack comprising an elongated flue tube adapted for mounting upright on a chimney top and having openings in its opposite sides oflset vertically, and a pair of deflector slats extending breadthwise across such respective openings and being generally inclined upwardly and inwardly from the opposite sides of said tube, the lower edges of said deflector slats being located substantially at the level of the lower edges of the respective tube side openings and being spaced substantlal distances inwardly from the tube sides and defining escape gaps therebetween for combustion products.

9. The chimney jack defined in claim 8, wherein the deflector slats slope inwardly and downwardly from their lower edge portions and thence inwardly and upwardly to their upper edge portions.

References Cited in the file of this patent UNITED STATES PATENTS 

